The present invention relates to a hydrogen producing device (reforming device) for producing gas containing hydrogen by use of air (, oxygen, or an oxidizing agent) and materials such as hydrocarbons and water, and a fuel cell power generation system using the hydrogen producing device.
As production processes for industrially producing hydrogen, various techniques are known. On page 221 of a document: Hiroo Tominaga and Masakazu Tamaki (supervision) “Chemical Reaction and Reactor Design” (Maruzen Co., Ltd. 1996), various processes or techniques such as: {circle around (1)} electrolysis of water; {circle around (2)} gasification of coal/coke; {circle around (3)} steam reforming of hydrocarbons; {circle around (4)} partial oxidation of hydrocarbons; and {circle around (5)} dehydrogenation of hydrocarbons, are shown. Historically, processes {circle around (1)} and {circle around (2)} are precursory, and processes {circle around (3)} and {circle around (4)} using petroleum hydrocarbons or natural gas hydrocarbons are becoming the mainstream at present.
Such processes have been developed mainly for producing hydrogen for ammonia synthesis, however, the processes are also being investigated as basic processes for hydrogen production for the application to fuel cell power generation systems. In fuel cell power generation systems, electric power is generated using hydrogen as a main material.
For example, in JP-A-2000-53403, a control method for a hydrogen production process, using an aqueous solution of methanol as a material and combining a steam reforming reaction with a partial oxidation reaction, has been disclosed. In the control method, the temperature of a reaction part is monitored and thereby the amount of oxygen to be supplied to the reaction part is calculated and determined in real time based on a theoretical reaction model considering the reaction heat. Generally, if the amount of the supplied material is controlled based on the theoretical reaction model, fine and precise reaction control (above all, stabilization of reaction temperature) becomes easier.
The stabilization of reaction temperature is especially important when a hydrogen production method called “combined reforming method (autothermal reforming method)” is employed.
The key feature of the combined reforming method is that a steam reforming reaction (endothermic reaction) is combined with a partial oxidation reaction (exothermic reaction) and suitable reaction temperature is maintained by keeping a proper balance between the two reactions. The proper balance between the reactions is realized by controlling the amounts of the supplied materials. Heat necessary for the reactions is autonomously supplied, and thus external heating means becomes unnecessary and consequently, simplification of the hydrogen producing device becomes possible and it is possible to make full use of the feature of the steam reforming reaction having high hydrogen production efficiency.
On the other hand, in order to make full use of the features of the combined reforming method, a method for controlling the amounts of the supplied materials capable of maintaining the proper reaction temperature under various practical environments where external perturbation is expected becomes necessary. Of course, it is needless to say that the stabilization of reaction is practically essential even when methods other than the combined reforming method are employed.
However, according to the control methods shown in the above references, the hardware necessary for the control inherently becomes sophisticated. Because, the sophisticated flow detection device and the sophisticated flow control devices become necessary in order to detect the flows of various materials and to carry out the fine and precise control based on the detected result. As a result, the cost for the whole system adds up, so that the application of the techniques is necessitated to be limited.
On the other hand, if the simple and easy flow detection and control of the supply amount and the simple and easy hardware associated therewith are employed for all the materials for the hydrogen production in order to reduce the cost, the stabilization of reaction becomes difficult in practical use. Especially, in the case where the combined reforming method is employed, the maintenance of the proper reaction temperature becomes difficult.